Set Appliance State:

Mains Power Off
On Off Switch ON (Switch flush with the fascia on the appliance)
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Does the display operate? (Information shown)
Note:
If a fault code is shown make a note of it at this point as the next test requires the boiler to be reset. Guidance on fault codes is given after the next test.